1. Field of the Invention
This invention relates to aminophenol urease inhibitors and urease inhibited urea based fertilizer compositions. More particularly, this invention relates to urease inhibited urea based fertilizer compositions which contain certain aminophenol compounds as urease inhibitors, and to methods and compositions for inhibiting the catalytic activity of urease through use of such aminophenol compounds.
2. The Prior Art
It is well known in the art to use urea and urea compositions in fertilizers, for application to the soil. The effective life of such fertilizers, however, is of short duration wherever microbiological activity exists in the soil to which the fertilizer is applied. This is due to the fact that urea is hydrolyzed rapidly, and nitrogen is lost in the form of ammonia, when urea is placed under or on the surface of soil which contains urease.
Urease, a crystallizable enzyme occurring in numerous bacteria and fungi, as for example Micrococcus urease, catalyzes the conversion of urea into ammonia and carbon dioxide. The reactions are as follows: ##STR1## A portion of the ammonia thus formed is held by absorbing constituents of the soil and is available to plants as nutrient. However, a large amount of the ammonia may be lost to the air. A further problem resulting from the action of urease is the rapid accumulation of ammonium in the soil which may result in damage to germinating seedlings and young plants.
One approach to the reduction of problems resulting from the activity of soil urease toward soil applied urea is to find compounds that inhibit urease activity when applied to soils in conjunction with fertilizer urea. This approach has received considerable attention, and several classes of compounds have been used. For example, Mishra, M. M. and Flaig, W., "Inhibition of Mineralization of Urea Nitrogen in Soil", Plant and Soil 51, pp. 301-309 (1979) discloses that 1,4-naphthoquinone; 2-methyl-1,4-naphthoquinone; 2,3-dichlorohydroquinone; 4,6-di-tert-butyl-o-benzoquinone; 4-tert-butyl pyrocatechol and 4,6-di-tert butypyrocatechol inhibit urease activity and nitrification. Similarly Bremner, J. M. and Douglas, L. A. "Effects of Some Urease Inhibitors in Urea Hydrolysis in Soils", Soil Sci. Soc. Amer. Proc., 37, pp. 225-226 (1973) reported that 2,5-dimethyl-p-benzoquinone, catechol, p-benzoquinone, hydroquinone, phenylmercuric acetate, N-ethylmaleimide, sodium p-chloromercuribenzoate, and acetohydroxamic acid, retard urea hydrolysis in soils and reduce gaseous loss of urea nitrogen. Also, Bremner, J. M. and Douglas, L. A. "Inhibition of Urease Activity in Soils", Soil Biol Biochem., 3, pp. 297-307 (1971), Mulvaney, R. L. and Bremner, J. M., "Use of p-Benzoquinone and Hydroquinone for Retardation for Urea Hydrolysis in Soils", Soil Biol Biochem., 10, pp. 297-302 (1978), and Quastel, J. H., "The Action of Polyhydric Phenols on Urease; the Influence of Thiol Compounds", Biochem. J. 27, pp 1116-1122 (1933), disclose the use of various polyhydroxy aromatic compounds as urease inhibitors.